The present invention relates to the domain of mail processing and more particularly to a secured accounting module for a franking machine.
It is known that the accounting module, which comprises in particular the reversible meters of a franking machine, is a sensitive element of this machine which must be protected against any fraudulent access. Now, the production of a module which is really physically tamperproof comes up against numerous technical problems.
In effect, firstly, the means for assembling the module must not be easily, or, better, must not be at all detectable from the outside. Secondly, once assembled, the module must be virtually non-dismountable. Lastly, if dismounting of the module were nonetheless attempted, it is important that any attempt at opening can be detected.
It is an object of the present invention to overcome the problems set forth hereinabove by proposing a secured accounting module of a particularly tamper-proof franking machine. Another object of the invention is to provide such impregnability simply and without requiring a complex process of manufacture.
These objects are attained by a secured accounting module of a franking machine comprising a printed circuit card intended to receive accounting circuits and mounted between a module base and a module cover, said base comprising a plurality of crimping studs on which said card is fitted and which are intended to cooperate with locking bushes fast with said cover, characterized in that it further comprises:
an insert ring interposed between each crimping stud and the corresponding locking bush
first connection means for connecting this insert ring with said cover, after said cover has been force-fitted on said base, and
second connection means for connecting this insert ring with said base, after said cover has been force-fitted on said base.
By this specific assembly structure which is produced internally, the assembly means cannot be detected from the outside, which makes it all the more difficult to disconnect them without causing destruction.
Said first connection means between said insert ring and said cover comprise a flange forming an integral part of said insert ring and intended to penetrate said locking bush when said cover is force-fitted on said base and said second connection means fast said insert ring and said base comprise an annular element forming an integral part of said crimping stud and intended to retain said insert ring by crimping, when said cover is force-fitted on said base. Said flange is preferably formed at the level of an end part of the insert ring.
Said locking bush advantageously comprises at its base a lug intended to cooperate with said annular element in order to move it apart and bend it against said insert ring.
Said insert ring is further provided with a transverse groove to give it sufficient elasticity when it is introduced in said locking bush. It is made of a material whose hardness is greater than that of the materials forming the base and the cover of the module. This material is preferably stainless steel.
According to an advantageous variant embodiment, the secured accounting module according to the invention may comprise areas of lesser resistance formed either around each of said locking bushes of the cover or around each of said crimping studs of the base and intended to break upon any attempt to separate said cover from said base.
The present invention also relates to a franking machine equipped with a secured accounting module.